Comprehensive treatment of marine aquaculture wastewater by a cost-effective flow-through electro-oxidation process

The effective treatment of marine aquaculture wastewater is of great significance to protect marine environment and marine organisms. This study validated the feasibility of the comprehensive removal of NH₄⁺-N, NO₂^--N, COD and P, as well as disinfection and antibiotics removal from marine aquaculture wastewater by electrochemical oxidation (EO), comparing the performance and energy consumption with that by electro-peroxone (EP) and electro-Fenton (EF) process. Due to the formation of more free chlorine, the removal of NH₄⁺-N and COD was in order of EO ≫ EP > EF. A new flow-through EO reactor was adopted, which was found enhanced the formation rate of free chlorine and degradation rate of pollutants, and thus performed better than that of flow-by reactor and batch reactor. By this flow-through EO process, the removal of NH₄⁺-N and NO₂^--N could reach >90% and their concentrations after treatment both meet the Water Drainage Standard for Sea Water Mariculture (SC/T 9103-2007). Meanwhile, the process had a good bactericidal performance with a lg(c/c₀) of -5.6. At the same time, antibiotics such as sulfadimidine (SMT) and norfloxacin (NOR) could be completely removed. The energy consumption was only 0.054 kWh/g NH₄⁺-N (0.27 kWh/m³), which was far more cost-effective than other oxidative processes. The new flow-through EO process has great practical application prospects for the comprehensive removal of multiple pollutants and sterilization from marine aquaculture wastewater.